So I have this X1 e84 2012. Usually I park in level surface and never had a chance to notice this. Recently I parked in a slightly sloped parking spot. As usual I pulled the handbrake two clicks and then put the car in P and I slowly lifted my foot off the brake and the car started moving slowly down the slope, I hit the brakes immediately. I tried re-engaging the hand break and took my foot off same thing happened but the brakes then caught on like after the car tyres had like a half rotation I would say. It was as if there was some delay between the main brake and the handbrake. I mean this could easily damage the car or cause damage to another car if I wasn’t paying attention. Any reason why this happens? Both the transmission (in park position) and the handbrake doesn’t engage or hold the car until after a slight movement. Other than this particular issue I haven’t noticed anything unusual with the brakes or the car in general.

Note: The car was serviced few months ago, had my brake pads and disks changed.